A welder works on one of the large steel braces that will support the new roadway while it's guided into position. Construction workers make final preparations on the Yerba Buena Island viaduct replacement project in San Francisco, Calif. on Wednesday, August 22, 2007. Caltrans will completely shut down the Bay Bridge over the Labor Day weekend to demolish the existing roadway and a new section rolled into place. PAUL CHINN/The Chronicle MANDATORY CREDIT FOR PHOTOGRAPHER AND S.F. CHRONICLE/NO SALES - MAGS OUT

Photo: PAUL CHINN

A welder works on one of the large steel braces that will support...

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Sam Brenes admires the view while construction workers make final preparations on the Yerba Buena Island viaduct replacement project in San Francisco, Calif. on Wednesday, August 22, 2007. Caltrans will completely shut down the Bay Bridge over the Labor Day weekend to demolish the existing roadway and a new section rolled into place. PAUL CHINN/The Chronicle
**Sam Brenes MANDATORY CREDIT FOR PHOTOGRAPHER AND S.F. CHRONICLE/NO SALES - MAGS OUT

Photo: PAUL CHINN

Sam Brenes admires the view while construction workers make final...

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Huge steel braces will support the new roadway when it is slowly rolled into position. Construction workers make final preparations on the Yerba Buena Island viaduct replacement project in San Francisco, Calif. on Wednesday, August 22, 2007. Caltrans will completely shut down the Bay Bridge over the Labor Day weekend to demolish the existing roadway and a new section rolled into place. PAUL CHINN/The Chronicle MANDATORY CREDIT FOR PHOTOGRAPHER AND S.F. CHRONICLE/NO SALES - MAGS OUT

By now, probably everyone west of the Rockies and south of Nome, Alaska, has heard that the Bay Bridge is going to be closed over Labor Day weekend.

If they haven't picked up one of the 600,000 glossy color brochures, then they've probably seen the message flashing on hundreds of electric signs in the Bay Area, Central Valley and Southern California. And if they missed those, they must have heard the radio advertisements or seen the television commercials. Or watched the ads that air just before the coming attractions at scores of movie theaters up and down the state. Even folks flying into Bay Area airports will be notified.

But for those who've been hiding in a cave or on a six-month world cruise: The bridge will close at 8 p.m. Friday and reopen no later than 5 a.m. Tuesday.

Caltrans has spent more than $500,000 getting the word out, said Bart Ney, the spokesman coordinating the effort, and the total is probably closing in on $1 million.

"It's been a statewide effort this time," he said. "With the whole bridge closed, we want to make sure everyone knows."

The Bay Bridge closure is also common knowledge in Tennessee, with about 10,000 orange-clad fans of the University of Tennessee Volunteers are expected to attend a sold-out football game against Cal at Memorial Stadium in Berkeley on Saturday.

When Ney called the university in Knoxville to inform them in April, the person he spoke with thought he was the victim of a college prank. But they've since taken the warning seriously.

"The team was going to stay in San Francisco, but because of the bridge, they're staying at the Claremont Hotel in Berkeley," said John Painter, a spokesman for the Tennessee football program. "A lot of fans and reporters are staying in San Francisco, and they're planning on taking BART."

Transportation officials hope Bay Area residents are also making plans in advance for how to get around without the only highway connecting the East Bay and San Francisco.

"The reason why we spend a half million to a million dollars on outreach is that we have to reduce the number of trips around the Bay Area - not just around the Bay Bridge," Ney said.

To drive people toward mass transit - and out of their cars - Caltrans is footing the bill for BART to run limited all-night service and for the Golden Gate and Alameda/Oakland ferries to run additional boats. BART will provide limited overnight service on Friday, Saturday and Sunday nights into the following mornings, as well as longer trains all weekend and extra trains for special events.

Overnight service will run hourly and serve 14 stations. Schedules and details are available at www.bart.gov. BART spokesman Linton Johnson advised people planning to ride the late night or early morning trains to think ahead and leave their cars at stations that will be open when they head home.

"We don't want people to get stranded," he said.

Transportation officials anticipate that the Golden Gate and San Mateo bridges will be forced to handle much of the traffic that usually crosses the Bay Bridge. While they're urging motorists to avoid driving if they can, they're also preparing. Caltrans will put extra toll collectors at the San Mateo Bridge. Golden Gate Bridge officials will add toll collectors and configure the bridge to maximize traffic flow, but authorities warn that Highway 101 backups are inevitable.

The district is urging people to take ferries - including special service between Larkspur and Sausalito - and buses, particularly a line that connects to the East Bay across the Richmond-San Rafael Bridge.

Caltrans and regional transportation officials will also set up a control center at Pier 7 at the Port of Oakland, where they'll monitor traffic around the Bay Area and try to react quickly to alleviate backups where possible.

Last Labor Day weekend, Caltrans closed the eastbound Bay Bridge for three days while it demolished a portion of the San Francisco approach and cleared away the rubble. Caltrans officials said they chose the holiday weekend because traffic tends to be lighter and few events are scheduled. The work went smoothly, there were relatively few traffic tie-ups, and the bridge reopened in time for the Tuesday back-to-work commute.

This year, the challenge is greater. Not only is the bridge closing in both directions, but more events also are scheduled in more locations around the bay. And the construction job that must be completed by Tuesday morning is far more daunting. Workers will demolish a 350-foot-long, 90-foot-wide section of the Bay Bridge known as the Yerba Buena viaduct and replace it with a new structure.

Contractor C.C. Myers - the Rancho Cordova (Sacramento County) firm that repaired the collapsed MacArthur Maze in 18 days - is doing the work. Workers already have built the new concrete piece just south of the bridge, where it rests atop temporary columns, waiting for the demolition.

Instead of using pneumatic hammers and wrecking equipment, crews will try to speed the demolition and cleanup process by using large concrete-saws to slice the existing bridge into 63 pieces. Then a huge crane will hoist the slabs onto trailers to be towed away by waiting trucks, Ney said.

"Everything is designed for ultimate efficiency," he said.

Once the demolition is complete, workers will use a unique roller system to push the new 6,500-ton viaduct into place. Rails will be installed beneath the structure, which will be lifted by jacks and slowly moved into position, and lowered onto permanent columns that have already been built. Then workers will apply the finishing touches and prepare it for the Tuesday morning commute.

"The thing that makes it really challenging for us is trying to get it done in three days," Ney said.

Caltrans officials had contemplated closing the bridge for a fourth day to make sure they had enough time. However, C.C. Myers and Caltrans' own studies assured them it was possible, albeit challenging, to get the job done in 81 hours.

Doing the work over Labor Day weekend is a gamble, Ney admitted.

"We have our lightest (weekend bridge) traffic over Labor Day weekend," he said. "But if we miss that window and go into the next week, we impact some of the busiest traffic of the year during the first week of September."

The reconstruction and retrofit of the Bay Bridge's east span are expected to cost about $6 billion and the span will open to traffic in both directions by 2013.